A torch bulb glows normally when a potential difference of 3.0V is applied across it and a current of 150mA flows through the filament.
(i) Calculate the resistance of the filament while the bulb is glowing.
(ii) The same bulb is now connected across a fully charged 4.5V battery. Assuming the resistance of the filament remains the same, determine the current that would flow through the bulb.
(iii) Briefly comment on whether the assumption made in part (ii) is strictly valid in practice.